Detect Network Device Authentication in Microsoft Sentinel
Adversaries may patch network device operating systems to add a hardcoded backdoor password, bypassing normal authentication for local accounts on routers, switches, and VPN appliances. SYNful Knock implanted a backdoor password in Cisco IOS router images, checking if login credentials match the backdoor password before passing them to normal authentication. SLOWPULSE modified Pulse Secure LDAP and 2FA authentication to accept a designated attacker-supplied password. Detection relies on network configuration integrity checks and unusual authentication behavior.
MITRE ATT&CK
- Technique
- T1556 Modify Authentication Process
- Sub-technique
- T1556.004 Network Device Authentication
- Canonical reference
- https://attack.mitre.org/techniques/T1556/004/
KQL Detection Query
// Network device authentication anomalies via syslog forwarded to Sentinel
Syslog
| where TimeGenerated > ago(24h)
| where Facility == "security" or SeverityLevel in ("warning", "error", "alert", "emergency")
| where SyslogMessage has_any (
"Authentication succeeded", "login successful", "accepted",
"incorrect password", "authentication failed"
)
| where HostName has_any ("router", "switch", "fw", "vpn", "asa", "ios", "junos", "nexus", "palo")
or SourceSystem == "Syslog"
| extend AuthResult = case(
SyslogMessage has_any ("succeeded", "successful", "accepted"), "SUCCESS",
SyslogMessage has_any ("failed", "incorrect", "denied"), "FAILURE",
"UNKNOWN"
)
| summarize TotalEvents=count(), Successes=countif(AuthResult=="SUCCESS"),
Failures=countif(AuthResult=="FAILURE"), UniqueUsers=dcount(ProcessName)
by HostName, Computer, bin(TimeGenerated, 1h)
| where Failures > 10 or (Successes > 5 and Failures == 0)
| sort by TimeGenerated descDetects suspicious authentication patterns on network devices forwarding syslog to Microsoft Sentinel. Monitors for high failure rates (brute-force testing of backdoor passwords) or unusually high success rates with zero failures (backdoor password working consistently). Targets Cisco IOS, Juniper, ASA, and other network device syslog messages.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate network administrators performing password rotation across multiple devices simultaneously
- Network monitoring tools (SolarWinds, PRTG, LibreNMS) using SNMP or SSH that generate authentication events during polling
- Automated configuration management tools (Ansible, Netmiko) running playbooks against multiple devices
- Network device failover events causing brief authentication spike as backup devices come online
Other platforms for T1556.004
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Verify Cisco IOS Image Hash (Integrity Check)
Expected signal: SSH authentication event in network device syslog. Network device syslog entry for privileged exec command execution. If syslog forwarding is configured, Splunk/Sentinel will capture the authentication and command events.
- Test 2Simulate Failed Network Device Authentication (Syslog Testing)
Expected signal: Network device syslog entries: 'Authentication failed for user testuser from <IP>'. If forwarded to SIEM: Splunk index=network_syslog with authentication failure events. Five events in rapid succession should trigger the failure rate detection.
- Test 3Check Network Device Syslog Collection
Expected signal: Test syslog message appearing in SIEM with source IP of the test host. The message mimics a Cisco IOS login success event and should match the network device authentication detection patterns.
References (5)
- https://attack.mitre.org/techniques/T1556/004/
- https://cloud.google.com/blog/topics/threat-intelligence/synful-knock-acis/
- https://tools.cisco.com/security/center/resources/integrity_assurance.html
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1556.004/T1556.004.md
- https://www.mandiant.com/resources/blog/mandiant-identifies-new-pulse-connect-secure-vulnerabilities
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